Switch for domestic appliances



Feb. 7, 2950 G. c. PEARCE Y SWITCH FOR DOMESTIC APPLIANCES File'd Feb. 13, 1946 4- SheetsSheet 1 (III ELECTRICAL-J msuuncm FIG. I

Feb. 7, 1950 G. c. PEARCE SWITCH FOR DOMESTIC APPLIANCES 4 Sheets-Sheet 2 Filed Feb. 13, 1946 FIG. 3

INVENTOR w 5 J 7 (f K1! W u 9 5 I\ 5 Q 34 MAN I I \b I I s 1 a V wm W1 I .w. m M 5 m Q /ll 8 3K Feb. 7, 1950 s. c. PEARCE SWITCH FOR DOMESTIC APPLIANCES 4 Sheets-Sheet 3 Filed Feb. 13, 1946 FIG.5

ELICTRICAL INUMTION Feb. 7, 1950 G. c. PEARCE 2,496,889

SWITCH FOR DOMESTIC APPLIANCES 4 Sheets-Sheet 4 Filed Feb. 1'5, 1946 Ill 23 I25 INVENTOR.

4. a; 24; FIG. u I

Patented Feb. 7, 1950 George C. Pearce, Dayton, Ohio, asslgnor to Generll ors Corporat on, Dayton, Ohio, a oor-' poration of Delaware Application February 18,1948, Serial No. 647.278

12 Claims. (01. sac-as) This invention relates to a domestic appliance and more particularly to controls for electric ranges and other applications.

3 Temperature controls for electric ovens must operate with accuracy over the wide range of temperatures preferably at a small difl'erential. In addition there has been a demand for the combination of the preheat, bake and brofl circuit switches with a temperature control arranged in such a way that the oven may be started in the preheat circuit if desired, and then circuits are automatically changed to the bake circuit arrangement when the selected baking temperature is reached, The devices of this type which have been used have the disadvantage that the automatic change from the preheat circuit to the bake circuit arrangement disturbs the operating temperatures oi. the temperature control during the first cycle and causes the over-shooting of the selected baking temperature.

It-is an object of my invention to provide a simple accurate oven control with an automatic preheat-bake circuit changing device which will not cause the over-shooting oi the selected temperature and which is controlled by a single knob.

It is another object of my invention to provide a simple accurate low difl'erential oven control which breaks both sides oi the supply conductors and requires no pig tail connections.

It is another object of my invention to provide a simple accurate oven control which can be readily adjusted by an ordinary serviceman.

It is another object of my invention to provide an oven control with a less expensive actuating means.

Briefly, to attain these objects I have provided an oven control with an adjustable disk-type diaphragm which, through a primary lever and toggle arrangement and an insulating tie bar, operates a dual toggle mechanism which opens and closes both sides of the supply conductors. The primary lever is provided with a projection cooperating with a recess in an arm of an auxiliary lever member, by which the auxiliary lever member is normally held in the bake position. A knob adjusts the position of. the diaphragm to obtain various baking temperatures and in addition operates a 'cam arrangement whereby the auxiliary lever may be operated to preheat position and the projection disengaged from the recess. When the oven approaches the proper temperature the projection will re-enter the recess thereby allowing the lever to return to the bake position. The control is made accuratethrough the use of kniie edges and cooperating notches 2 in the pivots of greatest movement oi the main switch mechanism. g

Further objects and advantages of the present invention will be apparent irom the following description, reierencebeing had to the accompanying drawings, wherein a'preferred form of the present invention is clearly shown.

In the drawings: Fig. 1 is a top view with an oven control embodying my invention;

Fig. 2 is a sectional view taken along the lines 2-2 0! Fig.1;

Pig. 3 is a sectional view taken along theline's oi the control with the Fig. '7 is a fragmentary view showing the preheat-broil control mechanism in preheating position;

Fig. 8 is a similar view showing the mechanism in the bake "01! cycle position:

Fig. 9 is a similar view showing the mechanism in the bake "on cycle position; v

Fig. 10 is a similar view showing the mechanism in the "01! position: and g Fig. 11 is a wiring diagram of the oven and control.

Referring now to the drawings, and more particularly to Fig. 2, there is shown an actuating diaphragm 2| iormedof an upper disk 22 having an upwardly flared rim and a lower disk 24 having a downwardly flared rim. These two disks 22 and 2 are soldered together at the base of their flared rim ,by a ring of solder II to form a sealed chamber between the disks. An annular bead 28 is provided in the lower disk adjacent its rim for improving the flexibility in expansion of the diaphragm. The downwardly turned annular bead in the upper disk 22 rests in the groove resulting from the formation of the bead 28. The lower disk 24 is. provided with a small central aperture and is bonded to a supporting member ll having passagestherein connecting this aperture with the tubing 82 which in turn connects to a suitable thermostat bulb suitably located within the oven 34 (see Fig. 11)

The bulb, the tubing 32, the member ll and the interior of the diaphragm 2| constitute a hydraulic assembly preferably fllled with some suitable iorm of liquid which expands and contracts substantially uniformly throughout the range of the cover removed oi taken along the lines auaeaa the control knob shaft 42. The knob shaft 42 is provided with a shoulder which bears against an adjustable gland nut 49 which is threaded into the pocket 43 riveted to the lower switch casing 99. The gland nut 49 has its outer periphery notched so that it is prevented from free movement by a spring latch 92. Also rigidly fastened to the knob shaft 42 is a disk 94 carrying a cam member 99.

The upper diaphragm 22 has bonded to it an operating button 93 which bears against the adjacent end of a primary lever 99. The primary lever is formed of a strip of metal with a rounded end over the button 99 and a projection 62 at the opposite end. The lever 99 also has lateral projections 94 provided with knife edges engaging notches formed in the pair of blocks 69 which are supported on the sheet metal base 69. The lever 99 is stiiiened by a thin metal member 10 which is turned up and notched to receive the hooked end 12 of a tension coil spring 14. The other end of the tension coil spring 14 is anchored to a U-shaped metal member 19 having outwardly extending prongs extending between the coils at the adjacent end of the spring 14. A tie 18 of electrical insulating material is provided with pins 39 having axially extending V-shaped notches. The tension of the spring 14 is adjusted by a set-screw 92 which extends through the yoke of the U-shaped member 19 and engages the middle of the tie 19. The movement of the pins 90 in the downward direction is interrupted by the conductor bars 84 and 99 and in the upward direction by the Z-shaped stop member 93 and 99. The notches in the pins 99 receive the knife edges formed on the separate knife edge members 99 which are riveted to the U-shaped contact strips 92 and 94 as shown in Fig. 6. The contact strip 92 is anchored to the post 99 as shown in Fig. 6, while contact strip 94 is similarly anchored to the post 99. The post 99 is mounted directly upon the end of the conductor 94. The knife edge members 90 are so beveled that the knife edge is at the face of the strip which is riveted to the contact member 92.

By this arrangement a direct column loading is applied to each of the thin metal strips forming the contact members 92 and 94 in the portion extending between the knife edge members 99 and the posts 96 and 99. Since the contact members 92 and 94 are very thin this column loading causes this portion of the strip to buckle and bend either upwardly or downwardly to the limits of movement of the pins III. The contact strip 92 is folded back beyond post 99 and carries a contact IIII at the end, which cooperates with the contactat the end of the conductor strip I03. Likewise the folded-back end of the contact strip 94 carries a contact which cooperates with the contact directly beneath it on the contact strip I99.

For illustrating the connection of my control to an oven circuit, I have shown such a circuit diagram in Fig. 11. As shown in Fig. 11, the conductor strip III3 is connected to one end of the lower heating unit I91 while the other end of the lower heating unit I91 is connected by the conductor I39 to the conductor strip III. The conductor strip I99 is connected by the conductor II3 to one end of the upper heating unit II9, the other end of which is connected to the neutral conductor of an Edison three wire power supply. A tap I2I connecting to the heating unit I I9 about one third the distance from the neutral end is connected by the conductor II1 to the conductor strip I I9.

The conductor strip III is normally connected by the bridge contact I23 to the arm I29 of the contact strip I99 to establish the baking circuit arrangement. For preheating, the conductor strip H9 is connected by the bridge contact I21 to the arm I29 of the conductor strip I93. For broiling, the bridge contact I21 remains closed but the bridge contact I 23 is opened.

According to my invention, for preheating both the switches I21 and I23 .are closed so that twothirds of the upper heating unit H9 and the entire lower heating unit I91 are energized at full line voltage with the switches 92 and 94 opening at the proper time to prevent the oven from being heated above the selected temperature and then reclosing when the temperature fails. The switch I21 is open while the switch I23 is closed A to establish the normal baking circuit in which the lower heating unit I91 is connected directly across the supply conductors at full voltage while the upper heating unit III has both portions connected in series between the conductor H3 and the neutral supply conductor N to cause it to be heated at a fraction of the supply line voltage. For broiling, the switch I23 is kept open while the switch I21 is kept closed. The switches 92 and 94 remain closed throughout the broiiing operation. This causes two-thirds of the upper heating unit II9 to be connected across the supply conductors at full voltage'with the remaining third being connected across one of the supply conductors and the neutral conductor N, while the lower unit I91 is entirely disconnected.

To operate the contact bridge I23, there is provided a vertical link I29 of insulating material, the upper end of which is provided with a shoulder upon which the contact bridge I23 rests as well as an ear through which extends a cotterpin I3I for locking the contact bridge I23 to the upper end of the link I29. The lower end of the link I29 is provided with an aperture I33 into which extends a projection I39 extending from one of the legs of a U-shaped member I31 pivoted upon the pivot pin I39 supported by a pair of arms I 4| extending downwardly from the sheet metal base 99. The link I29 is normally pushed downwardly by a very light coil spring I43. The other end of the U-shaped lever I31 is provided with a projection I49 extending through the aperture I41 in the link I49 of insulating material which at its upper end carries the contact bridge I21. This link I49 is also provided with a light coil spring I9I which tends to urge the contact bridge I21 against a pair of shoulders plainly shown on the link I49.

The dial knob I93 upon the end of the knob shaft 42 through the disk 94 and the cam member 99 operates the bell crank lever I99 when the knob I93 is in the highest temperature point of its operating range. The opposite end of the bell crank lever I99 carries a cam I91 which in the extreme high temperature position of the knob I93 engages the bottom of the vertical link I29 to lift the contact bridge I23 for deenergizing the lower heating element I91. As shown in Fig. 5

the U-shaped member I31 is lifted by its connection with the link I23 so that the projection at its opposite end lifts the link I33 to hold the bridge contacts I21 closed to connect the upper heating unit H5 directly into the circuit. In this position the control sets up the circuitfor broiling purposes which, with the contacts 32, 33 and I21 closed and the contact I23 open, connects twothirds of the upper heating unit II5, directly across both supply conductors and the other third between one of the supply conductors and the neutral conductor with the lower heating unit I31 being disconnected at one end from the supply conductor 36. Since the knob I53 is in its highest temperature position the switch contacts 32 and 33 will be held closed through the action of the toggle spring I3.

The U-shaped member I31 has fastened to it, by the set screw I53, a projecting member |6I provided with an aperture I63 which normally receives the projection 62 at the end of the primary lever as shown in Figs. 8 and 9. This projecting member is provided with a vertical slot I65 through which the screw I 53 extends into the yoke of the U-shaped member I31 to clamp this projecting member I6I to it. This screw I53 may be loosened and the vertical position of the projecting member I6I and its aperture I63 may be adjusted by the screw I61 which threads through the angle section I63 of the U-shaped member I31 and carries a pair of nuts Ill loosely positioned one on either side of the ear I13 extending from the projecting member I6I to hold its position relative to the U-shaped member I31. These nuts I" are fastened in place on the screw by solder. The projecting member I3I when the projection 62 isin the aperture I63, limits the extreme movements of the primary lever 63.

When, however, the knob I53 is turned to the broil position the U-shaped member I31 is moved to its extreme position shown in Fig. 2 whereby the projecting member IN is carried to the right as shown in Fig. 2 to disengage the projection 62 from the aperture I63. Since the knob I53 must be turned to its extreme high temperature position to cause the U-shaped member, I31 to be cammed to this "broil position, the threaded end portion of the knob shaft 32 must have pulled the nut 30 as well as the diaphragm assembly and the button 58 downwardly thereby allowing the toggle spring 13 to pull the long end of the primary lever 63 to its upper extreme position as shown in Fig. 7, in which the main contact mem-. bers 32 and 33 are closed.

After this is done the knob I53 maybe turned back to any of the baking positions, such as 400 F. for example, and the projection 62 will be contacted by the upper end of the projecting member I6I directly above the recess I63 thereby holding the U-shaped member in an intermediate position as shown in Fig. 7. In this intermediate position, the link I23 is lowered sufliciently to permit the contact bridge I23 to move to closed position and though the link I33 is likewise lowered, the spring I5I keeps the bridge contact I21 pushed up into its closed position. The primary lever 60 remains in this upp r position keeping the contact members 32 and 33 in the closed position until the selected temperature is reached for which the knob I53 is set. Thus all the switches are closed, connecting the circuits in the preheat arrangement with both the upper and the lower units H5 and I31 connected for maximum heating.

When the oven 33 approaches the proper temperature, the button33 will engage the short end of the primary lever 33 to move the projection 32 downwardly until it registers with and enters the aperture I33, after which under the continuing increase in heat the primary lever 63 and its projection 32 moves downwardly until the tripping point of the toggle mechanism is reached as illustrated in Fig. 8 to open the main contact members 32 and 33 to deenergize the entire cir- 'cuit. when the projection 62 enters the aper- I35, however, will pull the link I33 down far enough that the shoulders at the upper end of the link will carry the bridge contact I21 downwardly to open position. This will connect the circuit shown in Fig. 11 in the baking arrangement with the upper heating unit portions H6 connected in series with the neutral conductor at a fraction of maximum heat output and the lower heating unit I01 operating at maximum voltage and maximum heat output to provide uniform heating of the oven for baking purposes.

Inbaking position, the diaphragm member 20 will contract to cause the projection 62 to rise to the position shown in Fig. 9 causing the contact members 32 and 33 to be tripped to closed position. After sufficient heating in the baking circuit arrangement, the temperature rise will be suflicient to cause the diaphragm member 20 to expand to lower the projection 62 and the long end of the main lever to operate the toggle mechanism and the contacts 32 and 33 to the open position. The control will cycle in this manner throughout the baking period.

When the control is turned to the "off position, the button 53 will be moved high enough to force the long end of the lever 60 downwardly so that the projection 62 will be forced to the bottom of the aperture I63. This will cause the contact members 32 and. 33 to be moved to the open position thereby breaking both sides of the supply conductors. To give a positive feeling at the oil position, the disk 53 is provided with a. notch 53 between two projections which is adapted to receive the hump of the leaf spring 5| supported by a pair of pins extending into the switch casing 53.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A control including an actuating means, an anchorage, a plurality of thin metal strips arranged substantially parallel and each being tightlyfastened at one point to said anchorage, a tie transversely connecting the strips at a distance from the fastening point, said thin metal strips having an extension extending beyond the fastening point and provided with switch contacts, said contacts and fastening point being located adjacent opposite ends of the strips with the tie being located adjacent intermediate points of the strips, and spring means extending between said actuating means and said tie for applying a column load and for actuating said strips 7 anchorage, a plurality of thin metal strips arranged substantially parallel and each being tightly fastened at one point to said anchorage, a tie transversely connecting the strips at a distance from the fastening point, said thin metal strips having an extension greater in length than the distance between the tie and the fastenin point provided with switch contacts, said contacts and fastening point being located adjacent opposite ends of the strips with the tie being located adjacent intermediate points of the strips, and spring means extending from said tie beyond the fastening point to the actuating means for applying a column load and for actuating said strips.

3. A control including a movable actuating means, a pivoted cooperating device having an extending means extending substantially parallel to the movement of the actuating means, one of said means being provided with a projection and the other means being provided with a recess capable of receiving said projection and limiting the relative movement therebetween, means for operating said pivoted device to separate the projection from the recess to allow movement of the actuatinggmeans beyond the limit of movement provided by the projection within the recess, and a control device operated by the pivoted device.

4. A control including a movable actuating means, a pivoted cooperating device having an extending means extending substantially parallel to the movement of the actuating means, one of said means being provided with a projection and the other means being provided with a recess capable of receiving said projection and limiting the relative movement therebetween, means for operating said pivoted device to separate the projection from the recess to allow movement of the actuating means beyond the limit of movement provided by the projection within the recess, a control device operated by the pivoted device, and a second control device operated by said actuating means.

5. A control including a movable actuating means provided with a projection, a cooperating device having an extending means with a surface extending substantially transverse to the movement of the projection, the surface of said extending means being provided with a recess capable of receiving said projection and guiding said projection into said recess, means for moving said cooperating device away from said projection to disengage the recess from the projection and hold the cooperating device in a second position, and a control device operated by said cooperating device in its movement to and from said second position.

6. A control including a movable actuating means provided with a projection, a cooperating device having an extending means with a surfac extending substantially transverse to the movement of the projection, the surface of said extending means being provided with a recess capable of receiving said projection and guiding said projection into said recess, means for moving said cooperating device away from said projection to disengage the recess from the projection and hold the cooperating device in a second position, a control device operated by said cooperating device in its movement to and from said second position, and a second control device operably connected to and operated by said actuating means.

7. A control including an actuating means, an anchorage, a plurality of thin metal strips extending in one direction from the anchorage,

means forming a plurality of knife edges up n said strips, a tie having a plurality of notchu receiving said knife edges. and spring means extending between said tie and said actusting' means substantially in alignment with said strips for imposing a column loading thereon and for holding said knife edges in said notches, and a control device operated by said strips.

8. A control including an actuating means, a plurality of thin metal strips, a tie connecting the strips, a U-shaped member receiving the tie and provided with a set screw extending through the yoke into contact with the tie, spring means extending between said U-shaped member and the actuating means, and a control device operated by said metal strips.

9. A control including an actuating means provided with a projection, a snap-acting control device operatively connected to the actuating means, a rotatable means for adjusting said actuating means, a second control device having a recess cooperating with said projection for normally limiting the movement thereof, said second control device having guiding means adjacent the recess for guiding said projection into the recess upon movement of the actuating means, and means cooperating with said adjusting means for disengaging said projection from said recess to operate said second control device from one position to another.

10. A control including a casing having a stuffing box in a wall portion thereof, an actuating means within the casing, a control device within the casing connected to and operated by said actuating means, an adjusting shaft means extending through the stuffing box and having a threaded connection with the actuating means for adjusting the position of the actuating means. said adjusting shaft being provided with a shoulder adjacent the stufling box, said stuffing box being provided with an adjustable gland cooperating with the shoulder upon said adjusting shaft for controlling the location of the actuating means.

11. A control including an actuating means. an anchorage, a plurality of thin metal strips arranged substantially parallel, a tie transversely connecting the strips at an intermediate point, said strips being each tightly fastened to said anchorage at points spaced from said tie, said strips having extensions extending from said tie and provided with switch contacts, said contacts and fastening point being located adjacent opposlte ends of the strips with the tie being located adjacent intermediate pointsof the strips, and spring means extending from said tie beyond the fastening points to the actuating means for applying a column load and for actuating said strips.

12. A control including a movable actuating means, a movable cooperating device having an extending means substantially parallel to the movement of the actuating means, one of said means being provided with a projection and the other means being provided with a recess capable of receiving said projection and limiting the relative movement therebetween, adjusting means for adjusting the operation of the actuating means, means operated by said adjusting means for operating said movable device to separate the projection from the recess to allow movement of the actuating means beyond the limit of movement provided by the projection within the recess, and a control device operated by the movable device.

GEORGE C. PEARCE.

REFERENCES CITED Number '10 UNITED STATES PATENTS Ngme Date Urfer Dec. 15, 1931 Jennings Sept. 10, 1935 Clark Jan. 11, 1937 Newell July 9, 1946 

